(1) Field of the Invention
This invention relates to an anchorage for a webbing of a vehicle seat belt system, which serves to distribute an abrupt tensile force applied to the webbing to a stationary base of a vehicle.
(2) Description of the Related Art
Conventional anchorages for a webbing of a vehicle seat belt system include those capable of distributing an abrupt tensile force to a stationary base of a vehicle when an occupant is thrown forward and the abrupt tensile force is hence applied to the webbing in the event of abrupt braking or collision of the vehicle.
FIG. 3 is a fragmentary perspective view of one example of such anchorages, while FIG. 4 is a schematic perspective view showing its overall construction. Designated at numeral 11 in FIG. 4 is a seat, which is composed of a seat cushion 12 and a seat back 13. The seat cushion 12 is equipped with a seat slide upper rail 14, which is reciprocal along the seat slide lower rail 15 in the sliding directions of the seat 11. An anchor stay 16 is provided alongside the seat cushion 12 in such a way the anchor stay 16 extends in the sliding directions of the seat 11. A rear end portion 16a of the anchor stay 16 is fixed on a vehicle floor (not shown) by means of an unillustrated anchor bolt. The anchor stay 16 has a plurality of teeth 16b formed along the length of the anchor stay 16. The teeth 16b are engageable with a pin 18 of the base plate 17. A bracket 19 is attached to the seat slide upper rail 14 as depicted in FIG. 3. The bracket 19 is formed of a connected plate portion 19a and a raised plate portion 19b extending upright from the connected plate portion 19a. The connected plate portion 19a is fixed on the seat slide upper rail 14 by rivets 19e,19e. The base plate 17 is secured on the raised plate portion 19b. When an abrupt tensile force of at least a predetermined value is applied to a webbing 20 depicted in FIG. 4, the base plate 17 serves to transmit the abrupt tensile force to a stationary base of a vehicle by way of the anchor stay 16. The base plate 17 is reciprocated along the length of the anchor stay 16 in accordance with reciprocal sliding movements of the seat 11. Designated at numeral 21 is a guide portion of the base plate 17. A buckle 22 to which the webbing 20 is connected in use is pivotally secured to the base plate 17 by way of a buckle anchor 23. The base plate 17 is fixed on the raised plate portion 19b of the bracket 19 by rivets 17a,17a. Numeral 16c indicates a deformable resin cover interposed between the base plate 17 and anchor stay 16.
The connected plate portion 19a of the bracket 19 is composed of an extended front plate section 19c and a rear plate section 19d. The extended front plate section 19c is formed narrower compared with the rear plate section 19d. The raised plate portion 19b extends upright from the rear plate section 19d. The bracket 19 is riveted at the extended front plate section 19c. When an abrupt tensile force of at least said predetermined value is applied to the webbing 20, the abrupt tensile force is transmitted to the raised plate portion 19b via the base plate 17. As a consequence, the bracket 19 is deformed around the boundary between the rear plate section 19d and extended front plate section 19c in a direction indicated by arrow C, namely, in a direction that the rear plate section 19d is pulled away from the seat slide upper rail 14.
Since the brackets is deformed as described above upon application of the abrupt tensile force of at least said predetermined value to the webbing 20, the pin 18 is brought into engagement with one of the teeth 16b and the abrupt tensile force applied to the webbing 20 is hence distributed to the stationary base of the vehicle.
In order to ensure the prevention of any deformation by a tensile force smaller than the predetermined value in the conventional anchorage, the bracket 19 must have greater thickness and width. Corollary to this, a wider space is required to accommodate such a thick and wide bracket. It is also necessary to leave a space above the upper rail so that the bracket is allowed to move upwards when a force of said predetermined value or greater is applied to the webbing. The seat is usually located above the upper rail, thereby making it difficult to leave such a space for the upward movement of the bracket in many instances.